Frontal butt connection between two roof slab elements of a flat roof and corresponding roof slab element

ABSTRACT

The invention relates a frontal butt connection between two roof slab elements of a flat roof and to a corresponding roof slab element ( 1 ) which comprises undercuts, grooves or pockets ( 8, 9 ) integrated into its profile walls ( 6, 7 ). In this area the pockets of at least one roof slab element are substantially recessed in the form of slots ( 11 ) or a jog ( 15 ), and the apex of the slab can be removed. The slabs can be nested into one another or stacked without the pockets or grooves mutually impeding one another. Especially when the slots or the jog is configured in such a way that they almost halve the pockets next to the upper chord, the remaining pockets enclose the pockets of the subjacent slab. The top slab, in the slot area, is elastic to such an extent that it almost engages into the upper chord of the lower slab. The roof slab elements can be fastened, for example, in the area of the overlapping upper chords or with their slab surfaces resting on the purlin either with one another and/or on the purlin. The invention allows a gap-free butt connection of the roof slab elements despite their projecting pockets.

TECHNICAL FIELD OF THE INVENTION

The invention relates to a front-end connection between two roofingsheet elements for a flat roof and the corresponding suitable roofingsheet element that in its profiled walls comprises molded undercuts,grooves, or pockets, and the roofing sheet elements to be abutted havethe same profile cross-section with the same profile size.

STATE OF THE ART

Roofing sheet elements mostly have the form of sheets with trapezoidalcorrugation and with uniformly alternating protruding and recedingcreases that rest on the purlins of a flat roof, and are usually linedwith an insulating material and sealed with plastic or bitumen sheeting.The insulating and sealing materials are mechanically attached. Thisprocess is done with screws and large-surface load-distributing disks ora plastic-and-screw combination. A plastic-and-screw combinationconsists of a hollow shaft made of plastic, which retains a sunk-inscrew. The screw has a drilling tip that cuts into the roofing sheetelement. In the case of conventional roofing sheet elements, the screwspenetrate the roofing sheet in the area of the sheet's top cord and arevisible from the inner side of the building, which can bedisadvantageous not only for visual reasons, but also because thisdesign is prone to corrosion. In order to eliminate this flaw, theGerman patent specification DE 199 43 661 A1 describes an attachmentsystem in which the roofing sheet element comprises in its sides moldedpockets or grooves. The pockets of two parallel adjacent sheet sidesform a back-taper pair, which serves as a retaining means for theclamping lugs imbedded in the receding crease of the roofing sheetelement. The clamping lugs form a drillable working surface forattachment screws. The drilling bits penetrating the clamping lugsprotrude into the receding creases of the roofing sheet elements and areno longer visible from the inner side of the building. The roofing sheetelements of this form can no longer be installed so as to overlap in thebutt area, i.e., in transversal butt, because the pockets or groovesmolded in the sheet wall do not allow it. Such butt connections arecreated, e.g., with transition sheets.

The French patent FR 1 491 552 describes a sheet with trapezoidalcorrugation, which—in order to avoid drilling holes during theinstallation—are equipped with dents, in which attachments can beanchored. To allow assembly of the elements in a longitudinal direction,one end of the sheet with trapezoidal corrugation comprises a retainingprofile, which—by shaping the relevant end—is designed in such a mannerthat the flat, slightly expanding sections fit precisely against theflat sections of the adjacent element. The resulting butt joint istechnically demanding and costly, because the butt joint requires adeformation of the sheet elements and must be mechanically secured.However, this circumstance eliminates the original advantage of ascrew-free connection.

In addition, the specific protrusion of the sheet elements does notallow for free turning of the elements; rather, they must always be usedin one particular direction of installation. This problem results in arelatively high percentage of cuttings and thus in increased consumptionof the sheet material.

This invention proposes to solve the underlying technical problem bymeans of a simple and safe butt connection for roofing sheet elementsthat have molded undercuts, grooves, or pockets in their profiled walls.Furthermore, the task of this invention is to create a roofing sheetelement suitable for such a butt joint, wherein the roofing sheetelements to be abutted have the same profile cross-section with the sameprofile size.

REPRESENTATION OF THE INVENTION

To resolve the aforementioned technical problem, the invention proposesto overlap the roofing sheet elements in the area of the abuttingsurface and to arrange (in at least one of the roofing sheet elements orin the overlapping area) undercuts and pockets.

The particular advantages of this invention have to do with the roofingsheet elements, which can overlap in the abutting surface in theconventional manner. This possibility not only brings a static benefit,but it is also advantageous for the installation technology. The sheetscan both be inserted into each other and be shifted afterwards, andsimply laid on each other in order to create the abutting surface. Inspite of the proprietary profile cross-section, no special design needsto be used in the transversal abutting area. Thus, the invention allowsone to build a transversal butt joint with constructional overlap in thedirection of tension in the proven manner, which complies with theconditions of [the German industrial standard] DIN 18807, wherein thisinvention, for the first time, creates an abutting surface with modifiedsheets with pockets.

From the point of view of statics, the transversal butt serves only forthe transmission of transversal and/or support forces. Transmission ofthe bending moment is not intended. A special embodiment of thisinvention ensures that the roofing sheet of transversally abuttingdesign can be formed and dimensioned as and end support (abuttal) of aconventional non-slotted or non-notched sheet. Sheets designed accordingto this invention that are attached to the purlin (binding rafter) willprovide additional protection against suction forces created by thewind.

An advantageous embodiment of the invention comprises roofing sheetelements that will lie flatly on each other, at least in the area of thebottom cord. The pockets are designed in such a manner that they do notstick out and thus do not create any gaps in the overlapping area. Ifinstead of notching, where the top cord of the sheet is also removed, adouble-sided slotting is selected in order to remove the pockets, thenthe top cords also lie on the adjacent surface. The sheets can beinserted into one another or laid one on top of the other, without thepockets or grooves colliding with each other. Especially if, forexample, the slots are designed in such a manner that they approximatelyhalve the pockets close to the top cord, then the remaining full pocketsenvelope the pockets of the sheet lying below. The upper sheet iselastic in the slot area to such an extent that it slides into the topcord of the lower sheet. The roofing sheet elements can be attached,e.g., in the area of the overlapping top cords, either to each other orto the binding rafter. In a preferred design, the slots or the notchesextend from the front edge in the longitudinal direction of the roofingsheet element. With this design, the first sheet of the sheet band to becreated and installed does not need to be modified. Each following sheetrequires, on its front end, the fabrication of, e.g., the slotsaccording to this invention. The top cord located above the slot issupported by the top cord of the sheet lying underneath.

An advantageous embodiment of this invention comprises a notch in theroofing sheet element in the area of its undercuts, pockets, andgrooves. Since the top cord of the roofing sheet is not exposed to anystatic load, instead of the performed slotting it can be completelynotched or removed. Such slotting or notching can be optionallyperformed on the upper side of the bottom side of the sheet.

Furthermore, the invention provides a roofing sheet element for a buttjoint according to claim 1. Especially with an almost trapezoidalprofile cross-section (wherein its profiled wall sides comprise moldedundercuts, lugs, or pockets), the roofing sheet elements to be abuttedwill have the same profile cross-section with the same profile size, andwhich are characterized in that the roofing sheet elements comprise—onboth their sides in the area of the undercuts, lugs, and pockets—ofslots or a notched area that cut out the undercuts, lugs, or pockets toa large degree and that extend from the front edge in the longitudinaldirection of the roofing sheet element parallel to the sheet cord.

An advantageous embodiment of the invention comprises a notch in theroofing sheet element in the area of its undercuts, lugs, or pockets sothat the undercuts, lugs, or pockets including the sheet cord are mostlycut out and the notch runs from the front edge in the longitudinaldirection of the sheet. It is this design (with remaining or fullyremoved sheet cord that enables very flexible handling of the sheets ina real-life scenario. The sheets to be abutted can be pressed into eachother, or inserted into each other so that any required adjustment inlength is also possible.

Other advantages and advantageous embodiments of the invention willbecome clear from the following description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-section of the roofing sheet element according tothis invention

FIG. 2 shows the butt joint according to this invention in a side view

FIG. 3 shows a perspective view of the roofing sheet element accordingto this invention

FIG. 4 shows the front view of a test body

FIG. 5 shows the side view of the test body from FIG. 4

FIG. 6 shows a system outline of a test arrangement

FIG. 7 shows the bedding of the test objects in the cutout end

FIG. 8 shows a force displacement diagram of the examined sections ofsheets with trapezoidal corrugation (machine path s)

FIG. 9 shows a force displacement diagram of the examined sections ofsheets with trapezoidal corrugation (end abuttal displacement w)

FIG. 10 shows a summary of statistical evaluation of the ultimate loadsachieved.

FIGS. 11-13 indicate important dimensions of the tested sheets withtrapezoidal corrugation

FIG. 14 shows a schematic representation of the overlapping length inthe tension direction

FIG. 15 shows a side view that defines the length of the slotting

FIG. 16 shows a front view that defines the height of the slotting

FIG. 17 shows a table with the minimum widths of the abuttal zone

FIG. 18 shows a schematic representation of the arrangement ofadditional attachment means

INVENTION DESIGN EXAMPLE

The steel sheet with trapezoidal corrugation E 160 manufactured by thecompany Hoesch is used as the roofing sheet element 1. This steel sheetwith trapezoidal corrugation is subsequently cold-formed in the top cordin such a manner that it provides the option of attaching to thetrapezoidal sheet interlocking elements in a screw-free connection.

The roofing sheet element denoted with 1 consists of paralleltrapezoidal protruding and receding creases 3 and 4. In FIG. 1, the nextreceding crease 4 following the protruding crease 3 is only indirectlyindicated. The roofing sheet elements 1 and 2 are abutted withoverlapping areas that are denoted as 5. The roofing sheet elements 1, 2comprise pockets 8, 9, which are subsequently formed in their walls 6,7. Due to this special form, so far it has not been possible to performa conventional transversal abuttal with constructive overlapping in thestress direction in accordance with DIN 18807, Part 3, Paragraph 4.6.1.Therefore, according to this invention the roofing sheet element 1comprises a slot 11 in each of its walls 6, 7, which slot extends fromthe front edge 12 in the longitudinal direction of the sheet and whichapproximately halves the pockets 8, 9 so that they can be tilted overthe pockets 8′, 9′ lying above them. In the overlapping zone, theroofing sheet element 1 envelops the roofing sheet element 2 lyingunderneath, and both sheets fit closely together with their bottom cords13, 14 and/or their top cords 16, 17.

In order to prove the functionality of this invention, load tests wereperformed on sections of sheet with trapezoidal corrugation connected atthe butt joint. These tests will now be explained using the subsequentfigures. We used 2.5-meter long sections of modified steel sheet with atrapezoidal corrugation profile, in which—as shown in FIGS. 4 and 5—atone end the top cord was cut out at the length of about 25 cm and at thedepth of about 4 cm. The resultant notch is denoted with the reference15. The tests were performed in accordance with DIN 18807 as theso-called end-support tests under suction load. The required test designthat was used is essentially illustrated in FIGS. 6 and 7. This designcomplies in all essential details with the conditions of the relevantindustrial standards. The load was exerted by a servo-hydraulicallycontrolled 63-kN single test cylinder. The tests were performed in thedisplacement-controlled manner. The control parameter was thedisplacement speed of the test cylinder piston. The constantdisplacement speed was 0.08 mm/sec. The measured parameters were thepiston displacement (machine path S) and the resulting force F.Electrical signals were recorded using a PC, then further processed anddirectly plotted as force displacement curves.

FIG. 8 graphically illustrates the force displacement diagrams that weredetermined in four stress tests. FIG. 9 shows the results ofdisplacement measurements on the end support. The table in FIG. 10contains a summary of the statistical evaluation of the ultimate loadsachieved. FIGS. 11-13 contain the most important dimensions of thetested sheets with trapezoidal corrugation. The assessment of theinvention in connection with the performed stress tests went so far asto design a test focusing on total failure. This test had to be stoppedonly after all the screws were removed. Moreover, the tests demonstratedthat the reference values indicated for the constructive overlappinglength I₀ in the stress direction by DIN 18807 are decisive. Referencevalues of 50 to 150 mm apply to the overlapping length for a sub-shellmade of sheets with trapezoidal corrugation and with the upper sidesealing the roof. The length of the notch or slotting I₅ (FIG. 15)should correspond with the reference values for the overlapping lengthwith an additional extension that takes into account the extent of thepossible assembly gaps (FIG. 14) that are due to the necessary tolerancein installation. From the point of view of statics, the length of theslotting 15 (FIG. 15) and thus also of the alternative notch, i.e., acomplete removal of the top cord, is not relevant. As shown in FIG. 16,the slotting should be restricted to the zone of the pockets. Thebearing surface widths b_(A) of the elements according to the inventionin the zone of the transversal abuttal design (according to FIG. 14)comply with the minimum bearing surface widths of the end supports asper DIN 18807, Part 3, Paragraph 4.2.1., to the entirety of which weherewith refer. In slotted or notched sheets with trapezoidalcorrugation, due to the cross-section weakening, the minimum bearingsurface widths b_(A2) must be complied with from the end of the slot orthe notch along the entire un-weakened zone. The minimum bearing surfacewidth depends on the course of the installation. The underlyingnon-slotted or non-notched sheet with trapezoidal corrugation is notusually attached to the overlying sheet immediately after the laying.The overlying slotted or notched sheet with trapezoidal corrugation canbe attached immediately after the laying. FIG. 17 indicates therecommended minimum surface widths for the sheet with trapezoidalcorrugation according to the invention recommended by DIN 18807. As forthe connection means, relevant industrial standards or local governmentparameters prepared by the German Institute for Construction Technologyapply together with the provisions of DIN 18807, Part 3. According toDIN 18807, Part 3, the minimum distance of the means of connection fromthe transversal edge of the sheet with trapezoidal corrugation is:e≧20mm, e≧2×d with d=hole diameter.

Due to the cross-section weakening that can result in the case of highsuction stress, the connection of the slotted or notched sheet and theunderlying construction should be as close to the end of the slotting orthe notch as possible. Experimental verification has been performed withthe following distance of the connection means from the end of theslotting:e+s≦60 mmAs shown in FIG. 18, if for design reasons this distance cannot beadhered to, an additional attachment element should be arranged in theunweakened zone of the slotted or notched sheet with trapezoidalcorrugation. From the point of view of statics, arrangement of moreconnection elements is not necessary. However, additional constructionattachments such as the attachment of the remaining top cord to theunderlying trapezoidal sheet in the area of the slotting are possible.

All the features that have been indicated in the claims, thedescription, and in the drawings are essential for the invention on itsown and also in connection with other features. Front-end buttconnection between two roofing sheet elements for a flat roof and thecorresponding suitable roofing sheet element

1. Butt joint between two roofing sheet elements that compriseundercuts, lugs, or pockets formed in their profile walls, comprisingthe roofing sheet elements to be abutted, the roofing sheet elementshave the same profile cross-section with the same profile size, theroofing sheet elements that overlap each other in the abuttal zone andthe undercuts, lugs, or pockets of at least one of the roofing sheetelements are at least removed or cut out in the overlapping zone. 2.Butt joint according to claim 1, wherein the roofing sheet elements lieone on another, at least in the zone of the bottom cords.
 3. Butt jointaccording to claim 1, wherein the undercuts, lugs, or pockets are atleast partially removed by slots arranged in their area.
 4. Butt jointaccording to claim 1, wherein the undercuts, lugs, or pockets are atleast partially removed by a profile notch.
 5. Roofing sheet element fora butt joint according to claim 1, comprising undercuts, lugs, orpockets formed in their profile walls, wherein the roofing sheetelements to be abutted have the same profile cross-section with the sameprofile size, and on both sides in the zone of the undercuts, lugs, orpockets, the roofing sheet element comprises slots or a notch, whichremove the undercuts, lugs, or pockets to a large extent, and extendfrom the front edge in the longitudinal direction of the roofing sheetelement parallel to the sheet cord.
 6. Roofing sheet element accordingto claim 5, wherein, in the area of the undercuts, lugs or pockets, theroofing sheet element is cut out, including the sheet cord, so that theundercuts, lugs, or pockets are removed to a large extent, and thecut-out extends from the front edge in the longitudinal direction of theroofing sheet element parallel to the original sheet cord.
 7. Butt jointaccording to claim 2, wherein the undercuts, lugs, or pockets are atleast partially removed by slots arranged in their area.
 8. Butt jointaccording to claim 2, wherein the undercuts, lugs, or pockets are atleast partially removed by a profile notch.
 9. Butt joint according toclaim 3, wherein the undercuts, lugs, or pockets are at least partiallyremoved by a profile notch.
 10. Butt joint according to claim 7, whereinthe undercuts, lugs, or pockets are at least partially removed by aprofile notch.
 11. The roofing sheet element of claim 5, wherein theroofing sheet element has an almost trapezoidal profile cross-section.